The present invention relates to an image reading device installed in a copier, facsimile apparatus or similar image forming apparatus and, more particularly, to a device for reading a book document while turning the pages thereof and capable of surely detecting the edge of a page where the page begins to be turned over.
An automatic document feeder (ADF) is extensively used with an image forming apparatus of the kind described as an image reading device. The ADF automatically transports a sheet document to a reading position, reads the image of the document, and then discharges the document from the reading device. So far as the document is a sheet document, the ADF can read it automatically. However, when it comes to a book document, it is extremely difficult to automate the page turning operation of the ADF. The only measure left at the present stage of development is to turn the pages of a book manually. Although various methods and means have, of course, been proposed for reading a book document automatically, most of them are merely conceptual and far from practicality.
Conventional page turning devices may generally be classified into three different types, as follows. A first type of device causes a book document to be set in a spread position face down, and turns the page of the book by sucking it while moving the book document. A second type of device is similar to the first type of device except that the book document is spread face up. A third type of device is similar to the second type of device except that the suction is replaced with a roller, arm, etc. The first type of device, however, has a problem that the page turning operation suffers from a lack in reliability due to the weight of the book. In addition, this kind of approach undesirably rubs the spread surfaces of the book document. The problem with the second and third types of devices is that they each moves a space above the book document and, therefore, needs a bulky arrangement.
In light of the above, we have proposed a document reading device having a page turning device which is capable of surely turning the pages of a book document without increasing the physical size. The words "book document" refer to a document made up of a plurality of pages or leaves which are bound and can be spread, as needed. Our document reading device reads a spread book document while the page turning device turns over the page by receiving it in a page receiving section and then sending it out. A reflection type photosensor is mounted on the page receiving section for sensing the leaf being receiving therein. In response to the output of the photosensor, whether or not the leaf has been successfully accommodated in the receiving section on the elapse of a predetermined period of time after the beginning of a page turning movement is determined. If the answer of this decision is negative, it is determined that the page turning has failed. Further, whether or not the leaf has been successfully sent out from the receiving section in a predetermined period of time after the reception is determined. If it has not been discharged, it is determined that the discharge has failed.
The device described above, however, has some issue yet to be solved, as follows. Generally, the leaf of a book document entering the page receiving section is often curled or bent. Hence, when the leaf rises away from the inner periphery of the receiving section, the reflection of the photosensor changes depending on the position of the leading edge of the leaf. This prevents the ingress and egress of the leaf from the receiving section from being detected with accuracy. It follows that processing to be executed based on the output of the photosensor is inaccurate.